Characterisation of clinical carbapenem-resistant K1 Klebsiella quasipneumoniae subsp. similipneumoniae strains harbouring a virulence plasmid

The continuous emergence of carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-hvKP) poses a great challenge to human health owing to the associated extremely high morbidity and mortality. Klebsiella quasipneumoniae is a newly described bacterial species that is often misidentified as K. pneumoniae. Clinical K. quasipneumoniae strains have been reported worldwide, among which multidrug-resistant lineages have become a severe health problem, while less has been understood on this important pathogen. In this study, we characterised three clinical carbapenem-resistant K. quasipneumoniae subsp. similipneumoniae isolates belonging to sequence type 367 (ST367) and capsular type K1 and containing several virulence genes, including salmochelin (iroBCDN), aerobactin (iucABCDiutA) and regulator of mucoid phenotype (rmpA/A2), as well as some resistance genes, including blaKPC-2, blaTEM-1, blaOKP-B-9 and oqxAB. These carbapenem-resistant K. quasipneumoniae subsp. similipneumoniae strains containing virulence genes exhibited a higher level of virulence and serum resistance than a classical K. pneumoniae strain, while their virulence levels were slightly lower compared with typical ST11 CR-hvKP and ST23 K1 hvKP strains. This study reports for the first time the genetic and virulence characterisation of clinical K. quasipneumoniae subsp. similipneumoniae strains that simultaneously contained blaKPC-2 and virulence genes, contributing to a better understanding of their resistance and pathogenicity as well as for epidemic surveillance worldwide.